Gas sensor

Abstract

A gas sensor is proposed, which can detect a gas by a novel configuration while reduction in size is achieved. The gas sensor ( 1 ) does not need a light absorption path as in a prior art so that the size can be reduced correspondingly. Further, in the gas sensor ( 1 ), a gas is absorbed in an ionic liquid (IL), and a dielectric constant of the ionic liquid (IL) that changes by absorbing the gas can be measured according to a change in light intensity that occurs by a surface plasmon resonance phenomenon in a metal layer ( 7 ). Thus, the gas sensor ( 1 ) including the novel configuration that can detect a gas based on the change in the light intensity can be realized.

The invention claimed is: 
     
       1. A gas sensor that detects a gas that is a target of detection, comprising:
 a prism having a metal layer in an irradiation range of an incident light incident from a light source, and changing a path of the incident light at the metal layer to emit the incident light as an exit light; 
 a gas absorbing liquid provided on a surface of the metal layer, and capable of absorbing the gas; and 
 holding means covering the gas absorbing liquid, and causing the gas absorbing liquid to be held on the metal layer, 
 wherein a dielectric constant of the gas absorbing liquid changes due to absorption of the gas in the gas absorbing liquid, and based on a change in light intensity of the exit light by a surface plasmon resonance phenomenon that occurs in the metal layer in response to the change in the dielectric constant, the gas is detected, and 
 the holding means includes an internal space surrounded and formed by the surface of the metal layer, a wall portion, and a top plate portion having a plurality of through-holes bored therein, said wall portion being fixedly attached to the metal layer, so that the gas absorbing liquid is kept in the internal space while being exposed to an outside from the through-holes. 
 
     
     
       2. The gas sensor according to  claim 1 , wherein the gas is detected based on a change amount of a dip angle that occurs by the surface plasmon resonance phenomenon when the gas absorbing liquid absorbs the gas. 
     
     
       3. The gas sensor according to  claim 1 , wherein the gas is detected based on a change amount of reflection intensity that occurs by the surface plasmon resonance phenomenon when the gas absorbing liquid absorbs the gas. 
     
     
       4. The gas sensor according to  claim 1 , wherein the gas absorbing liquid in the internal space keeps staying in the holding means due to surface tension without leaking out from the through-holes. 
     
     
       5. The gas sensor according to  claim 1 , wherein the gas absorbing liquid is an ionic liquid. 
     
     
       6. The gas sensor according to  claim 1 , wherein the gas absorbing liquid is a hydroxide aqueous solution of an alkali metal and an alkaline earth metal. 
     
     
       7. The gas sensor according to  claim 1 , wherein the top plate portion and the wall portion are made of silicon. 
     
     
       8. The gas sensor according to  claim 1 , wherein the gas is CO 2  gas. 
     
     
       9. The gas sensor according to  claim 8 , wherein the gas absorbing liquid comprises an ionic liquid selected from the group consisting of [EMIM][BF 4 ], [BMIM][BF 4 ], [BMIM][PF 6 ], [Hmpy][Tf 2 N], [HMIM][Tf 2 N], [BMIM][Tf 2 N], [C 6 H 4 F 9 mim][Tf 2 N], [AMIM][BF 4 ], [Pabim][BF 4 ], [Am-im][DCA], [Am-im][BF 4 ], [BMIM][BF 4 ]+PVDF, [C 3 NH 2 mim][CF 6 SO 3 ]+PTFE, [C 3 NH 2 mim][Tf 2 N]+PTFE, [H 2 NC 3 H 6 mim][Tf 2 N]+cross-linked Nylon66, P[VBBI][BF 4 ], P[MABI][BF 4 ], P[VBBI][Tf 2 N], P[VBTMA][BF 4 ], and P[MATMA][BF 4 ]. 
     
     
       10. The gas sensor according to  claim 9 , wherein the gas absorbing liquid further comprises polyethyleneimine.